If you consider yourself a horror movie fan, chances are you've seen Hideo Nakata's Ring and Dark Water. They're superb, and Ring's making its way smoothly into Hollywood (maybe Dark Water will be adapted soon too?). While Ring is almost 100% pure heart pounding and nerve breaking, a tale of two sister is both nerve breaking and mind twisting.
Along with The Other I consider this Korean flick a brilliant and smart ending horror movie. The only flaw this movie has is some consider its first 20 minutes rather slow. It's actually typical with Korean and Japanese movies. I consider it carefully planned rather than slow, think of it as "calm moment before the storm". With thorough introduction of characters, imho viewer will get involved more intimately with the character, one of Korean and Japanese movies strongest point.
Like Ring, a tale of two sister doesn't overdo ghastly appearance. Rather they let our mind do the intimidating job itself. That way it's scarrier and horrifyingly classy at the same time. I won't be surprised if Hollywood remakes this movie after bringing Ring and Grudge/Ju-On over(This flick is not that good by the way, I rate it 5.5). Don't miss it!